Following up on Edward Snowden’s earlier claim that he could wiretap anybody as a low-level defense contractor—a claim denied by NSA officials and House Intelligence Committee Chairman Mike Rogers—Glenn Greenwald appeared on This Week With George Stephanopoulos and claimed that his forthcoming reporting would prove exactly that.

“It’s an incredibly powerful and invasive tool,” Greenwald said of the program Snowden used, “exactly the type that Mr. Snowden described. NSA officials are going to be testifying before the Senate on Wednesday, and I defy them to deny that these programs work exactly as I’ve just said.”

Greenwald described the capabilities of the program, accessible not just by NSA officials but by low-level private contractors:

“The NSA has trillions of telephone calls and email in their databases. What these programs are are very simple screens, like the ones that supermarket clerks or shipping and receiving clerks use, where all an analyst has to do is enter an email address or an IP address, and it does two things: it searches that database and lets them listen to the calls or read the emails of everything that the NSA has stored, or look at the browsing histories or Google search terms that you’ve entered; and it also alerts them to any further activity that people connected to that email address or connected to that IP address do in the future. And it’s all done with no need to go to a court, with no need to even get supervisor approval on the part of the analyst.”

Greenwald noted that while “there are legal constraints on how you can spy on Americans,” there’s nothing stopping, or even detecting, abuse of the program.

“The real issue here is that what the NSA does is done in complete secrecy,” Greenwald said. “Nobody really monitors who they’re eavesdropping on. The question of abuse is one that the Congress ought to be investigating much more aggressively.”

Greenwald also pointed out that, if true, these allegations would make some under-oath statements from the likes of National Intelligence Director James Clapper untrue.

“One of the most amazing parts of this entire episode has been that top-level national security officials like James Clapper really did get caught lying red-handed to the American Congress about what the NSA is doing,” Greenwald said. “It’s amazing that he not only hasn’t been prosecuted, but he stil has his job. What that does is it lets national security officials continue to lie to the public.”